module Tins::Deflect

def deflect_start(from, id, deflector)
  @@sync.synchronize do
    Deflect.deflecting ||= DeflectorCollection.new
    Deflect.deflecting.member?(from, id) and
      raise DeflectError, "#{from}##{id} is already deflected"
    Deflect.deflecting.add(from, id, deflector)
    from.class_eval do
      define_method(id) do |*args|
        if Deflect.deflecting and d = Deflect.deflecting.find(self.class, id)
          d.call(self, id, *args)
        else
          super(*args)
        end
      end
    end
  end
end